Segmented Thermocouple Housing for Combustor Temperature Sensing
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Solution Overview
Problem
Existing exhaust gas temperature sensors in gas turbine engines face challenges in accurately measuring high-temperature exhaust gases due to the rigidity and service limit constraints of thermocouple elements, often requiring placement downstream of the combustor, which leads to inaccurate fuel input optimization and component life estimation.
Innovation Solution
A temperature sensing device with a housing configured to envelop the sensor, allowing a portion to be outside and receiving a flow of cooling air, providing structural support and accurate temperature measurement within the combustion chamber.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If smaller diameter thermocouple elements are used to increase reactance, then measurement precision is improved, but the rigidity to resist drag from exhaust gas flow deteriorates
Solution Approach 1:
The thermocouple element is segmented into two functional zones: a smaller diameter sensing portion (0.020-0.040 inches) for accurate temperature measurement, and a larger diameter support portion (0.060-0.125 inches) for structural rigidity. This segmentation allows each portion to be optimized for its specific function while working together as an integrated element.
Solution Approach 2:
Different portions of the thermocouple element have different diameters tailored to their local requirements. The distal sensing portion has a smaller diameter for measurement precision, while the proximal support portion has a larger diameter for mechanical strength. This local quality variation resolves the contradiction between measurement precision and structural rigidity.
2Reliability
If thermocouple elements are placed downstream of the combustor to avoid thermal stress, then the reliability of the sensor is improved, but the measurement precision of exhaust gas temperature deteriorates due to using estimated temperatures
Solution Approach 1:
The service limit temperature parameter of the thermocouple element is increased from typical values (around 1800-2000°F) to at least 2300°F through material selection and design. This parameter change enables direct placement in the combustor where temperatures exceed 2300°F, eliminating the need for downstream estimation and providing direct, accurate measurements at the source.
3Temperature
If higher temperature rated alloys are used for the housing, then the service limit temperature is improved, but the cost and manufacturing complexity increase
Solution Approach 1:
The housing employs a composite construction combining a heat-resistant alloy outer shell (Inconel 600 or 625) for thermal protection with a ceramic inner liner (alumina or silica) for direct contact with hot gases. This composite material approach achieves high temperature resistance (2300°F+) while managing manufacturing complexity through standardized components and assembly procedures.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enables accurate temperature measurement of combustion gases at high temperatures, optimizing fuel input and extending the life of engine components by directly inserting the sensor into the combustion chamber, thereby improving engine efficiency and reducing operational costs.
Implementation Method 1
The housing is configured to receive a flow of cooling air
Data Source
AI summary
A method of assembling a temperature sensing device for a gas turbine engine is provided. The method includes providing a temperature sensor and providing a housing configured to envelop the temperature sensor. The method further includes mounting the temperature sensor within the housing such that a portion of the temperature sensor is disposed outside of the housing and such that the housing is configured to receive a flow of cooling air.